1. Field of the Invention
The present invention relates to a multi-stylus recording head fit for use as an electrostatic recording head and a process for producing the same. More particularly, the present invention relates to improvements in the structure and method of connecting the recording electrodes of a multi-stylus recording head to a wiring board.
2. Related Art
A multi-stylus recording head, for example, a same-side control type multi-stylus recording head for use in an electrostatic recording system generally has, as shown in FIGS. 14 and 15, two rows of recording electrodes 101, 102 formed with conductors 108 arranged densely in the form of a cross-stitch with a constant pitch, and two rows of control electrodes 103, 104 corresponding to the recording electrodes 101, 102, the recording and control electrodes being fixedly incorporated in an electrode support block 105 of insulating resin. For example, with M (e.g., 128) pieces as one set, M.times.N (e.g., 55)=7,040 pieces of the first electrodes 101, M.times.N (=7,040) pieces of the second electrodes 102 arranged in parallel to the first ones with a predetermined space held therebetween, and the control electrodes 103, 104 arranged along and outside the respective rows of the first and second recording electrodes 101, 102, are provided so that each of the edge faces of the control electrodes 103, 104 is exposed on the surface of the electrode support block 105 of the insulating resin.
In this case, the leading end portions of the conductors 108 normally form the first and second recording electrodes 101, 102, respectively. In order to simplify the driving circuit required, the conductors 108 of the recording electrodes are grouped together and each group is connected to a wiring board 106 once before being connected to the driving circuit. In the case of the first recording electrodes amounting to M.times.N pieces, for example, N pieces of conductors 108 of the recording electrodes which belong to the same group are collected out of the N sets of recording electrode groups and soldered to one terminal 107 of the wiring board 106, so that the conductors 108 are put together in the M pieces of terminals. On the other hand, the second recording electrodes 102 are also grouped together before being soldered to the opposite side of the wiring board 106 (not shown). The terminals 107, . . . , 107 are connected via connectors (not shown) to the driving circuit, whereby voltage is applicable to any given recording electrodes 101, 101.
The recording electrodes of the multi-stylus recording head and the terminals on the wiring board are wired in the relation shown in FIG. 16. For example, the leftmost recording electrode 101 of the conductor 108 is connected to the first terminal 107; the second recording electrode 101 to the second terminal 107; and then the third recording electrode 101 to the third terminal 107. In this manner, the 1st-128th recording electrodes are each connected to the 1st-128th terminals 107 successively, and then the 129th-256th recording electrodes are each connected to the 1st-128th terminals 107, . . . , 107 successively. This process is repeated N times so as to distribute M.times.N (=7,040) pieces of recording electrodes 101 among the terminals 107, . . . , 107 in 128 places for wiring purposes.
With the conventional wiring structure, 7,040 pieces of conductors 108 are stacked up while being made to cross each other between the electrode support block 105 and the terminals 107, so that the whole (7,040 pieces) is formed into a layer 109 like a sheet of woven stuff as shown in FIG. 14. As to the second recording electrodes 102, moreover, these are wound like in the same order before being formed into a layer 109 like woven stuff. Consequently, the conductors 108, 108 of the two adjoining recording electrodes are positioned too closely; the problem is that the floating electrostatic capacitance tends to grow large. When the electrostatic floating capacitance is large, it is known that good recording is impossible because the applied voltage drops and because the driving voltage waveform becomes dull. In a recording pattern called an intermediate planar image where about half the electrodes alternately repeat recording.cndot.non-recording (ON.cndot.OFF) as shown in FIGS. 17(A) and (B), the pattern will be affected seriously by the floating electrostatic capacitance due to the dropping of the applied voltage.
In this case, the dropping of the applied voltage is caused by the fact that the current flows from the ON recording electrode side to the OFF recording electrode side along the path of the floating electrostatic capacitive coupling. More specifically, the dropping of the applied voltage is caused by the following mechanism:
1) The recording electrodes 101, . . . , 101 of the multi-stylus recording head and its driving circuit are arranged in a push-pull circuit system as shown in FIG. 18. When the recording electrode 101 is OFF (non-printing), for example, an upper-stage driver IC111 is turned on and a lower-stage driver IC112 is turned off so as to hold the recording electrode 101 at the ground potential. When the adjoining recording electrode 101 is ON (printing) then, an upper driver IC113 is turned off and a lower driver IC114 is turned on, whereby -260 V, for example, is applied to the recording electrode 101.
2) At this time, there arises a difference in voltage between both the recording electrodes 101, 101 and both the conductors 108, 108 and the current route created then allows the current to flow so as to charge a kind of capacitor 115 as the electrostatic floating capacitance formed therebetween.
3) An excessive current flows at the time the driver pulse rises and the applied voltage is dropped as the current causes the applied power to be excessive in capacitance.
As shown in FIG. 19 indicating the dependence of the effective applied voltage on the floating electrostatic capacitance at the time a pattern is drawn 0011!, the greater the dropping degree of the applied voltage is, the greater the floating electrostatic capacitance grows. Because of the large floating electrostatic capacitance, the conventional multi-stylus recording head has been able to deal with line drawings having a low printing percentage but not with recording planar images having a relatively large printing percentage.